feature(service): Implements traffic splitting and tagging targets

 - Add e2e tests
 - Use '=' for traffic and tag assignment instead of ':'
 - Use --tag and --untag flags for tagging traffic targets
 - Use --traffic flag for setting traffic portions
 - Allow --traffic portion to either take revisionName or tagName
 - Uses @latest identifier for referencing latest revision of service
 - Dont throw error if requested revision=tag pair is same
 - Support having multiple tags for a revision
	 - creates a new target in traffic block if revision present in traffic block with new tag requested
	 - creates N new targets in traffic block if revision absent in traffic block with Nxnew tags requested
 - Ensure updating tag of @latest requires --untag flag
	 - streamline updating tag for latestReadyRevision
	 - adds respective tests
	 - adds tests for ensuring given traffic sum to 100 on CLI and fail fast
 - Add note about preference of order in case where tagOfOneRevision == revisionOfAnother,
   first tags are checked and assigned traffic if any, as tags are supposed to be
   unique in traffic block and should be referenced in such scenario.
 - Remove the examples from flag description, moves it to service update command example section
 - Pass only traffic block to compute trffic, makes it better to consume.
 - Cover more error cases for invalid value format for assignments, covers a=b=c, a=, =b, or variants of them
 - Separate and improves the error messages
 - Add unit tests for traffic computing
 - Add sanity checks in dedicated function verifyInputSanity
 	  - traffic perents should sum to 100
          - individual percent should be in 0-100
          - repetition of @latest or tagName or revisionRef is disallowed
 - Verify traffic percents sum to 100 on client side and fail fast
 - Add e2e tests for traffic splitting
	 - create and update service, assign tags and set traffic to make an existing state
	 - run the scenario on existing state of service
	 - form the desired state traffic block
	 - extract the traffic block and form the traffic block struct actual state
	 - assert.DeepEqual actual and desired traffic blocks
 - Use logic to generate service name in the same way as namespace, use different service name per test case
 - Run e2e test for traffic splitting in parallel
 - Use timeout duration of 30m for e2e tests, use timeout parameter for go_test_e2e library function
 - Use tagName in flag description of --untag, avoiding conflict with --tag flag

docs/cmd/kn_service_update.md

@@ -14,14 +14,25 @@ kn service update NAME [flags]
 
 ```
 
-  # Updates a service 'mysvc' with new environment variables
-  kn service update mysvc --env KEY1=VALUE1 --env KEY2=VALUE2
+  # Updates a service 'svc' with new environment variables
+  kn service update svc --env KEY1=VALUE1 --env KEY2=VALUE2
 
-  # Update a service 'mysvc' with new port
-  kn service update mysvc --port 80
+  # Update a service 'svc' with new port
+  kn service update svc --port 80
 
-  # Updates a service 'mysvc' with new requests and limits parameters
-  kn service update mysvc --requests-cpu 500m --limits-memory 1024Mi
+  # Updates a service 'svc' with new requests and limits parameters
+  kn service update svc --requests-cpu 500m --limits-memory 1024Mi
+
+  # Assign tag 'latest' and 'stable' to revisions 'echo-v2' and 'echo-v1' respectively
+  kn service update svc --tag echo-v2=latest --tag echo-v1=stable
+  OR
+  kn service update svc --tag echo-v2=latest,echo-v1=stable
+
+  # Update tag from 'testing' to 'staging' for latest ready revision of service
+  kn service update svc --untag testing --tag @latest=staging
+
+  # Add tag 'test' to echo-v3 revision with 10% traffic and rest to latest ready revision of service
+  kn service update svc --tag echo-v3=test --traffic test=10,@latest=90
 ```
 
 ### Options
@@ -43,6 +54,9 @@ kn service update NAME [flags]
       --requests-cpu string      The requested CPU (e.g., 250m).
       --requests-memory string   The requested memory (e.g., 64Mi).
       --revision-name string     The revision name to set. Must start with the service name and a dash as a prefix. Empty revision name will result in the server generating a name for the revision. Accepts golang templates, allowing {{.Service}} for the service name, {{.Generation}} for the generation, and {{.Random [n]}} for n random consonants. (default "{{.Service}}-{{.Random 5}}-{{.Generation}}")
+      --tag strings              Set tag (format: --tag revisionRef=tagName) where revisionRef can be a revision or '@latest' string representing latest ready revision. This flag can be specified multiple times.
+      --traffic strings          Set traffic distribution (format: --traffic revisionRef=percent) where revisionRef can be a revision or a tag or '@latest' string representing latest ready revision. This flag can be given multiple times with percent summing up to 100%.
+      --untag strings            Untag revision (format: --untag tagName). This flag can be spcified multiple times.
       --wait-timeout int         Seconds to wait before giving up on waiting for service to be ready. (default 60)
 ```
 

pkg/kn/commands/flags/traffic.go

@@ -0,0 +1,56 @@
+// Copyright © 2019 The Knative Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package flags
+
+import (
+	"github.com/spf13/cobra"
+)
+
+type Traffic struct {
+	RevisionsPercentages []string
+	RevisionsTags        []string
+	UntagRevisions       []string
+}
+
+func (t *Traffic) Add(cmd *cobra.Command) {
+	cmd.Flags().StringSliceVar(&t.RevisionsPercentages,
+		"traffic",
+		nil,
+		"Set traffic distribution (format: --traffic revisionRef=percent) where revisionRef can be a revision or a tag or '@latest' string "+
+			"representing latest ready revision. This flag can be given multiple times with percent summing up to 100%.")
+
+	cmd.Flags().StringSliceVar(&t.RevisionsTags,
+		"tag",
+		nil,
+		"Set tag (format: --tag revisionRef=tagName) where revisionRef can be a revision or '@latest' string representing latest ready revision. "+
+			"This flag can be specified multiple times.")
+
+	cmd.Flags().StringSliceVar(&t.UntagRevisions,
+		"untag",
+		nil,
+		"Untag revision (format: --untag tagName). This flag can be spcified multiple times.")
+}
+
+func (t *Traffic) PercentagesChanged(cmd *cobra.Command) bool {
+	return cmd.Flags().Changed("traffic")
+}
+
+func (t *Traffic) TagsChanged(cmd *cobra.Command) bool {
+	return cmd.Flags().Changed("tag") || cmd.Flags().Changed("untag")
+}
+
+func (t *Traffic) Changed(cmd *cobra.Command) bool {
+	return t.PercentagesChanged(cmd) || t.TagsChanged(cmd)
+}

pkg/kn/commands/service/service_update.go

@@ -18,6 +18,8 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/knative/client/pkg/kn/commands/flags"
+	"github.com/knative/client/pkg/kn/traffic"
 	"github.com/spf13/cobra"
 	api_errors "k8s.io/apimachinery/pkg/api/errors"
 
@@ -27,19 +29,30 @@ import (
 func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var editFlags ConfigurationEditFlags
 	var waitFlags commands.WaitFlags
-
+	var trafficFlags flags.Traffic
 	serviceUpdateCommand := &cobra.Command{
 		Use:   "update NAME [flags]",
 		Short: "Update a service.",
 		Example: `
-  # Updates a service 'mysvc' with new environment variables
-  kn service update mysvc --env KEY1=VALUE1 --env KEY2=VALUE2
+  # Updates a service 'svc' with new environment variables
+  kn service update svc --env KEY1=VALUE1 --env KEY2=VALUE2
+
+  # Update a service 'svc' with new port
+  kn service update svc --port 80
+
+  # Updates a service 'svc' with new requests and limits parameters
+  kn service update svc --requests-cpu 500m --limits-memory 1024Mi
 
-  # Update a service 'mysvc' with new port
-  kn service update mysvc --port 80
+  # Assign tag 'latest' and 'stable' to revisions 'echo-v2' and 'echo-v1' respectively
+  kn service update svc --tag echo-v2=latest --tag echo-v1=stable
+  OR
+  kn service update svc --tag echo-v2=latest,echo-v1=stable
 
-  # Updates a service 'mysvc' with new requests and limits parameters
-  kn service update mysvc --requests-cpu 500m --limits-memory 1024Mi`,
+  # Update tag from 'testing' to 'staging' for latest ready revision of service
+  kn service update svc --untag testing --tag @latest=staging
+
+  # Add tag 'test' to echo-v3 revision with 10% traffic and rest to latest ready revision of service
+  kn service update svc --tag echo-v3=test --traffic test=10,@latest=90`,
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
 			if len(args) != 1 {
 				return errors.New("requires the service name.")
@@ -69,6 +82,15 @@ func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 					return err
 				}
 
+				if trafficFlags.Changed(cmd) {
+					traffic, err := traffic.Compute(cmd, service.Spec.Traffic, &trafficFlags)
+					if err != nil {
+						return err
+					}
+
+					service.Spec.Traffic = traffic
+				}
+
 				err = client.UpdateService(service)
 				if err != nil {
 					// Retry to update when a resource version conflict exists
@@ -99,6 +121,7 @@ func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 	commands.AddNamespaceFlags(serviceUpdateCommand.Flags(), false)
 	editFlags.AddUpdateFlags(serviceUpdateCommand)
 	waitFlags.AddConditionWaitFlags(serviceUpdateCommand, 60, "Update", "service")
+	trafficFlags.Add(serviceUpdateCommand)
 	return serviceUpdateCommand
 }